1. Field of the Invention
The present invention relates to a liquid crystal display device, an image displaying method, and an image displaying program. More specifically, the present invention relates to a liquid crystal display device, an image displaying method, and an image displaying program, which can suppress deformations and after-images that are generated in moving images.
2. Description of the Related Art
A liquid crystal display (LCD) is a system for displaying moving pictures through switching the screen by each frame. However, unlike an impulse-type display device such as a CRT (cathode ray tube), the LCD is a hold-type display device where an image is held within a frame period. Thus, it has such shortcomings that blur, deformations and distortions of the image are generated in a moving video.
In the case of the impulse-type display device, an image is displayed as a pulse at the initial stage within a frame, which provides a black display until the next frame. Thus, the after-image recognized by the eyes of a user can be adjusted.
In the case of the hold-type display device, an image is held and displayed as a still picture within a frame period. Therefore, even though the eyes of the user follow a moving body smoothly from a frame to a next frame, the image being displayed stays still during the frame period and the frame shifts to the next continuously without a break. Therefore, the frame one before appears as an after-image to the user, so that the user perceives a double image where those shifted images are overlapped with each other. Thus, the user recognizes “blur”. Such “blur” caused due to the eye-trace of the user in the hold-type display device will be described by referring to FIG. 12.
FIG. 12(1) shows a case where a dark-color line moves in a bright background, and FIG. 12(2) shows a case where a bright line moves in a dark background. FIG. 12(b) shows changes in time of one line that moves on a screen as in FIG. 12(a). The display system of a liquid crystal panel employs a hold-type drive, so that the same display is maintained within one frame period and the frame is shifted discontinuously. Meanwhile, the eyes of the user continuously follow a scroll of the screen as in “eye-trace” shown in FIG. 12(b). FIG. 12(c) shows the shift of the image in a coordinate system on the basis of eye-trace of the user.
On the basis of the eye-trace of the user, the image minutely oscillates by one-frame cycle. As shown in FIG. 12(d), the user recognizes a leveled luminance of the oscillations, thereby recognizing “blur”.
In order to overcome such inconvenience, Japanese Unexamined Patent Publication 2002-23707 (Patent Document 1) discloses such contents that: one frame is divided into a plurality of sub-frames; an image based on an input luminance signal is displayed in a preceding sub-frame; and an image based on a signal that is obtained by dividing the input luminance signal by an attenuation coefficient is displayed in a following sub-frame.
A display device depicted in Patent Document 1 adjusts the after-image perceived by the eyes of the user through providing a period (where the image with the attenuated luminance is displayed) in one frame so as to decrease the “blur” that is caused due to the eye-trace of the user in the hold-type display device.
However, separately from the after-image perceived by the eyes of the user, the response speed of the liquid crystal has something to do with the “blur” that is a failure in expressing a moving picture in a liquid crystal display unit of a hold-type display device.
As can be seen from FIG. 12, regarding the “blur” caused due to the eye-trace of the user, the sizes of the “blur” recognized by the user are the same for the case where a dark-color line moves in a bright background and for the case where a bright line moves in a dark background.
The response speed of the liquid crystal panel differs between the time of applying a drive voltage and the time of discharging the voltage, due to a delay in the transition speed which is caused by the viscosity of the liquid crystal, a delay in starting the response which is caused by an overshoot drive, and the like. Also, the response speed differs depending on the transition of the gradations (from which gradation to which gradation), so the response of the liquid crystal becomes ununiform. Meanwhile, the blur generated in the moving picture caused due to the hold-type drive of the liquid crystal panel and the eye-trace of a human being is uniform and constant. Therefore, in the related art, the widths of the blur in the moving pictures differ depending on the image to be shifted, which provides a deformed and distorted image and generates a colored blur.